The 3rd Generation mobile communication system (IMT-2000) and the evolved system thereof, i.e. future mobile communication system, are designed to be an advanced mobile communication system capable of overcoming the main disadvantage of the first Generation and 2nd Generation mobile communication system thoroughly. An outstanding feature of the 3rd Generation communication system is to enable a personal terminal user to realize high-quality mobile communication and transmission of any information, with any person, in any way, at any time and at any place in the worldwide, in the future mobile communication system.
The 3rd Generation mobile communication system mainly consists of TD-SCDMA formulated by China, CDMA2000 formulated by the U.S.A. and WCDMA formulated by Europe. CDMA2000 Standard is widely used in North America and many other places around the world, and in order to further improve the CDMA2000 Standard, the evolved standards of CDMA2000 have been formulated: CDMA2000 EV/DO and CDMA2000 EV/DV.
In EV/DO system, EBCMCS (Enhanced BroadCast MultiCast Service) is proposed, and the EBCMCS system is mainly used to transmit broadcast message to mobile stations in a whole coverage area. The architecture of EBCMCS channel is illustrated in FIG. 1: firstly, perform channel coding on the data information input, while the channel coding is ⅕ or ⅓ Turbo coding 101, then, perform channel scrambling, interleaving, repeating and punching 102 on the data been coded, dividing the coded data into two ways of I and Q through 16 QAM (quadrature Amplitude Modulation) 103, and perform OFDM (Orthogonal Frequency Division Multiplexing) modulating process on the two ways of I and Q respectively, then the data passes through quadrature PN (Pseudo-random Noise) de-spreading module 108, and perform time-division multiplexing on the data and pilot and MAC (Media Access Control) information, as shown in FIG. 2, and finally, sending the data through quadrature PN spreading module 203 with Base Station (BS for short) information. Wherein, the OFDM modulation module comprises mainly: inserting guard interval and pilot module 104, QPSK (quadrature Phase Shift Keying) spreading module 105, IFFT (Inverse Fast Fourier Transform) module 106, and inserting cyclic prefix module 107. Wherein, the QPSK spreading module 105 mainly functions to reduce the Peak-to-Average Ratio of OFDM.
In EBCMCS, to make it convenient for the mobile station to demodulate broadcast information, in the previous downlink, information about the BS, which is added to the sending sequence through the quadrature PN spreading module, needs to be shielded. Therefore, before each timeslot is generated, a quadrature PN de-spreading module needs to be added, and as shown in FIG. 1 and FIG. 2, perform quadrature PN de-spreading processing to the data information input, and then input the data information to the TDM (Time Division Multiplexing) module and perform time-division multiplexing with Pilot Channel and MAC information, and finally, add a BS identifier through the quadrature PN spreading module, to form and send a complete timeslot. The simplified block diagram of the whole transmitting end is shown in FIG. 2.
The quadrature PN spreading mode is explained in the EBCMCS Protocol (3GPP2 C.S0054-A Version 1.0 cdma2000 High Rate Broadcast Multicast Packet Data Air Interface Specification of 3GPP2). deep research on the quadrature PN de-spreading mode has been made, and a new quadrature PN de-spreading mode is proposed in this application.